Zinc is a ubiquitous element that is physiologically important to normal human function. However, zinc exposure can result in multiple consequential toxicities that are dependent on the dose and route. The typical systems affected are the respiratory, hematopoietic, and neurologic. Recent medical literature has contributed to the current knowledge of these effects.
The Babylonians used zinc alloys more than 5000 years ago,1 and references to zinc oxide as a lotion to heal lesions around the eye can be found in the Ebers papyrus, written in 1500 B.C.15 Zinc oxide and zinc sulfate were used in Western Europe during the late 1700s and early 1800s for gleet (urethral discharge), vaginal exudates, and convulsions. In the late 1800s, brass workers who inhaled zinc oxide fumes were noted to develop "zinc fever," "brass founders' ague," and "smelter shakes," all of which are now identified as metal fume fever (Chap. 124).57
Throughout history, humans have contaminated the environment with zinc. For example, release of zinc and other metals from mines produces elevated concentrations of zinc in the local water supply and vegetation, which may lead to elevated tissue zinc concentrations and clinical effects in the nearby population.40,51
The antiinflammatory effects of zinc sulfate were studied with mixed results in the late 1970s for acnevulgaris. However, a double-blinded controlled study found no difference between zinc and placebo.63 The more recent use of zinc supplementation as an alternative preventive and treatment strategy is exposing large numbers of patients to undefined risks for unclear benefits.
Zinc, a transition metal, has two common oxidation states, Zn0 (elemental or metallic) and Zn2+. Like other transition metals iron (Chap. 40) and copper (Chap. 93), zinc participates in reactions that result in the generation of reactive oxygen species. Such as superoxide radicals or hydroxyl radicals which can damage both local and remote tissues (Chapter 11).
The pure element exists as a blue to white shiny metal, but it also combines with other elements to form many compounds: zinc chloride (ZnCl2), zinc oxide (ZnO), zinc sulfate (ZnSO4), and zinc sulfide (ZnS). Once the metal is exposed to moisture, it becomes coated with zinc oxide or carbonate (ZnCO3).71
Zinc is an essential nutrient and found in more than 200 metalloenzymes, including acid phosphatase, alkaline phosphatase, alcohol dehydrogenase, carbonic anhydrase, superoxide dismutase, and DNA and RNA polymerases.71 Zinc contributes to gene expression and chelates with either cysteine or histidine in a tetrahedral configuration, forming looped structures known as zinc fingers, which bind to specific DNA regions.8,87 Other functions of zinc include membrane stabilization, vitamin A metabolism, and the development and maintenance of the nervous system. Zinc and copper concentrations generally have an inverse relationship in the serum with elevated ...